In general, dust collectors are essentially used to prevent environmental pollution by exhaust gas, fine particulate matter, industrial waste, etc., which are exhausted at the manufactories or factories of manufacturing or processing cement, fiber, chemical, metal, etc. A centrifugal force dust collector by cyclone or a filtration dust collector by a filter bag is chiefly used as the dust collector according to a dust collection method.
In particular, a dust collection capability and size and weight of a filtration dust collector are determined by a filter bag that is incorporated in the inside of the filtration dust collector. The filter bag is formed of an outer circumferential surface of a smooth cylindrical shape. Here, a number of filter bags are housed in the dust collector. The filter bag is made using a material such as polyester, polypropylene, nylon or DuPont's TEFLON™ products according to the chemical and physical properties, a service temperature, and features of a dust collection target. The number of incorporated filter bags is changed according to a desired filtering efficiency. As the numbers of filter bags becomes large, size of a dust collector becomes large, and thus a large facility area is needed. Accordingly, filter bags are manufactured to increase the surface area on the outer circumference in order to improve a filtering efficiency in the filter bag of an identical size. A bellows style filter bag will be described with reference to FIG. 1.
As shown in FIG. 1 a filter bag 10 includes a cylindrical filter cloth 11 of a bellows shape in which a number of peak portions 12 and dale portions 13 are formed in the lengthy direction on the outer circumferential surface of the filter bag 10. As shown in FIG. 1 the filter bag 10 includes upper and lower caps 15 and 16 which are adhered to the upper and lower portions of the filter cloth 11, respectively, to support the filter cloth 11, and a venturi tube 14 which is coupled on the upper end of the filter cloth 11 penetrating through the upper cap 15, and pressurizes an air pressure of air which spurts into the inside of the filter cloth 11.
Since the bellows style filter bag 10 having the above-described structure is formed of a relatively extensive surface area on which filtering can be done in comparison with a filter bag having an non-corrugated smooth surface on the filter cloth 11, it is known that a filter efficiency is increased. However, it is very troublesome to manufacture the bellows style filter bag 10 so as to form bellows or maintain the formed bellows to be kept consistently according to quality of the material of the filter cloth 11. Accordingly, a particular material such as polyester can be used as the filter cloth 11. As a result, there is a demerit that a dust collection target or a use place where the filter bag 10 can be used is limited. An example of limiting the dust collection target or the use place will be described. Since polyester is very weak chemically in alkalinity, it is not so good to use polyester in the place where alkaline particulate matters are exhausted. Meanwhile, polypropylene is strong in alkalinity, but is not difficult to form corrugation or maintain the formed corrugation continuously according to quality of the material. Accordingly, although polypropylene has several advantages in comparison with polyester, polypropylene has a limitation on manufacture that polypropylene is not easily used as the filter cloth 11 of the bellows style filter bag 10. When manufacturing the general filter bags having a smooth surface, a filter cage is provided in order to support a filter cloth, and the filter cloth is supported on the filter cage and sewn. Meanwhile, when manufacturing the bellows style filter bag 10, the filter cloth 11 is generally adhered to the upper and lower caps 15 and 16 by an adhesive since the bellows style filter bag 10 has the difficulty in sewing the filter cloth 11 onto the upper and lower caps 15 and 16 in view of feature in its shape of the bellows style filter bag 10. If the filter cloth 11 is adhered to the upper and lower caps 15 and 16 by the adhesive, the adhesion portion is very weak at a high temperature or in a damp place. For this reason, if the filter bag 10 is used under the high temperature or damp condition, life-time of the filter bag 10 is shortened. In addition, the mesh of the filter cloth 11 becomes relatively small at the corrugated dale portions 13 of the filter bag 10. Accordingly, a blinding phenomenon occurs by the dust, to thereby lower a dust collection efficiency. In the case that dust adhered on the surface of the filter cloth 11 is removed, a dust removal efficiency is lowered. Accordingly, the lifetime of the filter bag 10 is greatly shortened.